Superconductivity, superstructure, and structure anomalies in Mg1-xAlxB2 -: art. no. 132505

The presence of a superstructure is identified to play a key role for the modifications in both superconductivity and structure transitions in the Mg1-xAlxB2 system. This superstructure occurs along the c-axis direction, and can be well interpreted by Al-layer ordering. The optimal composition of the superstructure phase is MgAlB4, a superconductor with T(c)similar to12 K. Raman spectrum of MgAlB4 gives rise to a sharp peak at around 941 cm(-1). Brief diagrams illustrating the superconductivity and structural features of Mg1-xAlxB2 (0less than or equal toxless than or equal to1) materials are presented.